Brake shoe manufacture



Aug. 8, 1933. R B PGUE 1,921,836

BRAKE SHOE MANUFACTURE Filed Jan. 4, 1952 Invenor: 5- C@ s 5f. 2M

Patented Aug. 8, 1933 UNITED STATES BRAKE SHQE MANUFACTURE Robert B.Pogue, @ra-nge, N. J., assigner to The American Brake Shoe and FoundryCompany, Viilmlngton, Del., a Qorporation of Delaware ApplicationJanuary 4, 1932. Serial No. 584,740

i1 claims. (C1. 18s-258) This invention relates to that class ofcomposite brake shoes in which reenforces of some kind are embedded inthe cast iron body during the casting operation.

Heretofore it has been the practice to embed a ductile metal reenforce,commonly called a steel back, in the back of the cast iron body of ashoe to hold the parts of the body together in case of fracture so thatthe shoe may continue in service. The backs comprise rods, bars orplates and the plates have been per orated, slotted or cut out in avariety of skeleton forms. lt `has been proposed also to make the backsof expanded -`etal and other mesh material. It has also been thepractice to provide reenforces such as bundles of expanded metal whichare placed in the mold and embedded in the cast iron body of the shoe tohold the parts of the body together in case of fracture so that the shoemay continue in service and for other purposes, and sometimes thesebundles are arranged so that the expanded metal vextends to the back ofthe body. These recnforces have been used separately and they have beenused together, and in many different forms. The reenforces have beenlightly coated 'f ith refractory material by dipping them in oil andallowing them to drain and then dipping the reenforces in silica hour orother such refractory material. Suicient silica hour adheres to theoiled surface of the reenforce to form a light coating which has beensufficient under the general conditions of manufacture to protect thereenforce from burning and losing its natural physical characteristicsduring the casting operation. The reeniorce is arranged in the mold andthe hot metal to form the body is then poured into the mold. If thereenforce is not protected, it may burn or carb-onine under the heat ofthe hot metal and partially unite with the cast iron, making thereenforce brittle so that it is liable to break when the shoe fracturesand at the point of fracture. When the reenforce is protected, it doesnot become united in this way with the cast iron body but it is firmlyheld by the cast iron body in intimate contact therewith throughout itslength and under this condition it will break at the fracture in thebody before, and sometimes long before, the body is worn out. This isdue to the fact that the area of the reenforce which is freed by thefracture from intimate contact with the cast iron of the body isconcentrated at the fracture and does not extend any appreciabledistance into the body away from the fracture. The shoe is arcuate inshape and is ordinarily suspended in substantially upright 5 position inservice, and therefore the vibrations to which the shoe is subjected inservice will affect only that part of the reenforce which is freed fromintimate contact with the body at the fracture. The reenforce breaksbecause of fatigue of metal which causes crystallization, and thisfatigue is the result of at least four major conditions,-compression,tension, bending and vibration of the reenforce. Compression, tensionand bending resultvfrom brake application. Bending also results fromimpact of the shoe against the wheel when the brake rigging is caused toswing which mostly occurs in switching service but also occurs in trainoperation. Vibration occurs in the loose end of the shoe Whenever thecar is in motion and this vibration varies in intensity according totrack conditions and is transmitted to the reenforce.' lThe compression,tension, bending and vibration strainsare concentrated in the reenforceat the fracture of the body if the reenforce is rigidly held in the bodyat the fracture and under these conditions the reenforce will breakrelatively quickly. The reenforce Within the body of the shoe Will breakmore quickly than a reenforce in the back of the shoe and this isespecially true if the reenforce Within the body is a bundle of expandedmetal. The body of the shoe will break rst, then the reenforce Withinthe body of the shoe will break, and, finally, if the shoe is providedwith a reenforce back, the reenforce back will break. If a part of theshoe then falls away, as frequently happens, the efficiency and serviceof the shoe will be reduced and the detached part may lodge in a frog ora switch and cause derailment of a train or bounceA off of the track andcause injury to person and damage to property. y

My invention has for its object to control these causes of breaking inthe reenforce or reenforces and to distribute the effect thereof over aconsiderable area of the reenforce so that the shoe will have a chanceto Wear out in service before any part becomes detached. I have foundthat if the reenforce or reenforces are not united with and are not inintimate contact with the body of the shoe, the effect of vibration andbraking strains is relieved to the extent that breaking of the reenforceis delayed, and this delay is in direct proportion to the length of thereenforce over which the vibration and braking strains are distributed,and from this I have determined that it is not desirable to hold thereenforce or reenforces rigid in the body at any point. Inlaccomplishing this result, I treat the reenforces in a novel mannerpreparatory to embedment in the body so that they will be free fromintimate contact with the body throughout their length. I do not mean bythis that the reenforce should be loose so that it may rattle in thebody or so that it may have any relative movement in the body When theshoe is at rest. rIhe conformation of the reenforce and the body is suchthat, even when the reenforce is not in intimate contact With the bodyas it has been in previous manufacture, it will be anchored in placesuiiiciently to prevent rattling or relative movement or such a degreeof looseness as would be indicated thereby.

In the accompanying drawing I have illustrated the invention in a plaincar shoe in which Fig. l is a side View of the shoepartly broken awayand in section.

Fig. 2 is a plan View of a ductile metal reenforce back.

Fig. 3 is a longitudinal sectional view of an expanded metal reenforce.

Fig. 4 is a sectional View on the line 1 -4 of Fig, 1 showing a shoewith a ductile metal reenforce back and an expanded metal reenforce.

The shoe selected for illustration comprises a cast iron body 5, aductile metal reenforce back 6, a ductile metal lug strap 7, and aplurality of layers of expanded metal arranged in a bundie 8 and forminga reenforce which is embedded in the body between the wearing face andthe back and beneath the reenforce back 6. The body and the reenforceback and the reenforce 8 may be made in any desired form and of anysuitable material and embedded in any type of brake shoe for which theyare or may be adapted. The shoe illustrated is provided with end lugs 9as an integral part of the body and the metal of the lugs is anchoredover the ends of the reenforce back and through the slots 10 or otheropenings in the back with the main part of the body so that thereenforce back is securely held to the cast iron body of the shoe. Thelug strap '7 is of well-known form and the body metal is run up in aknown manner at the sides of the strap. The expanded metal reenforce islwholly embedded in the body of this type of shoe but it may be exposedat the sides and at the wearing face of the body. The reenforce back maybe omitted and sufficient additional layers of expanded metal may beprovided in the bundle 8 to serve the purpose of a reenforce back, andthe expanded metal may be exposed at the back of the shoe if desired.

According to my invention, the reenforces are not united with the castiron body, nor are they so intimately in contact with the body as tomake them rigidly and firmly held therein. I accomplish this bysubjecting the reenfcrces to a preparatory treatment before placing themin the molds for the casting operation. This treatment may beaccomplished by giving the reenforces a coating of oil and silica flourin or about the manner heretofore described but if this method isfollowed the coating must be considerably thicker to accomplish theobjects of my invention. A preferred treatment, as disclosed inY myapplication Serial No. 584,741, filed concurrently herewith, consists incoating the reenforce with oil of high viscosity having low carboncontent and lowV sulphur, such as black lubricating oil known to thetrade as summer and winter black, then to give the reenforce a coatingof refractory material, such as silica flour, by dippingl it in theflour or in any other suitable manner, and then to bake the coatedreenforce in an oven such as a core oven. I have found it desirable tostart with a temperature of about 350 F. and continue the baking stepfor about thirty minutes. By this method the reenforce is provided witha tough semi-enamel coating which adheres tightly to the reenforce andproduces a highly satisfactory protection during the casting operationwhich insures that the reenforce will not become united with the castiron body and will not be firmly and rigidly held in intimate Contacttherewith in the completed shoe. I prefer to apply the coating accordingto either method throughout the area of the reenforce, and this mayinclude, if desired, the lug strap. The purpose of the treatment of thereenforce is to prevent the cast iron of the body from uniting with thereenforce during the casting operation, or from having such intimatecontact with the reenforce that the latter will be held rigidly andfirmly in the body. The oil which forms the bond of the coating willburn out under the high heat of the molten metal durirrT the castingoperation leaving the refractory material unbonded and in adisintegrated state and forming a cushion for the reenforce where itremains therea'oout but liable to sift out of the shoe through anyavailable opening during movement of the shoe under the conditions ofhandling and service. It is the intention of the invention that thereenforce shall not be rigidly and irmly held in intimate contact withthe body but that it shall be embedded in the body so that it will befree from intimate contact with the body but anchored therewith. I donot mean that the reenforce should be out of contact throughout itslength with the body because there may be contact, and always will be incommercial manufacture, between the reenforce and the body but not thatintimate Contact which has been characteristic of brake shoes heretoforemade and which effects a firm and rigid embedment of the reenforce inthe body. To comply with my invention and to secure to the fullestextent the beneficial advantages thereof, the reenforce must be freefrom, by which I mean out of intimate contact with, the body suriciently to permit vibration and braking strains at a fracture in thebody to be distributed remotely in the reenforce from the fracture inthe body. This will prevent the compression, tension, bending andvibration strains Yfrom being concentrated upon the reenforc'e at thefracture and permit these strains to be distributed along the reenforcein both directions and away from the fracture. By thus distributing thestrains over a considerable area of the reenforce, instead ofconcentrating them at the line of fracture, the fatigue of the metal isvery materially retarded and so much retarded that the body of the shoewill wear down to the limit of wear before the'reenforce breaks. Anykind of reenforce will have openings or recesses or some configurationto insure anchorage of the body to the reenforce and prevent parts fromfalling away immediately in case of fracture and the purpose of thisinvention is to prevent the reenforce from breaking and allowing a partof the shoe to fall away before the shoe wears out in service. In thecaseof a reenforce consisting of bundle of expanded metal, it may bethat some strands of the expanded metal will break before they arereached in the wear of the shoe but generally speaking there will besufficient expanded metal remaining to function in accordance with myinvention and there will always be expanded metal at the back of theshoe or some other type of reenforce at the back of the shoe to functionin accordance With my invention even though the expanded metal in theWearing part of the shoe is broken before the limit of wear of the shoeis reached. So that a shoe provided with a reenforce at the back andwith or without a reenforce in the wearing part of the body will remainin service under general conditions until the limit of Wear of the shoehas been reached. As I have said before, there must be an anchorage ofthe reenforce with the body, as there has been in practice heretofore,but this anchorage must not involve a union of the reenforce and thebody or such an intimate Contact of the reenforce with the body as Willresult in a concentration of strains upon the reenforce at a fracture inthe body. The reenforce must be suiflciently free from the body, andpreferably throughout its length, to permit strains upon the reenforceresulting from a fracture in the body to be distributed through thereenforce over a considerable area thereof away from the fracture toretard the fatiguing effects which vibration and other strains upon thereenforce would impose. In this way the brake shoe will be enabled toperform in the manner and for the period expected of it.

I do not limit the invention to any particular kind of brake shoe orreenforce or to the particular methods of treating the reenforce hereindescribed and I reserve the right to maireany changes therein within thescope of the following claims.

I claim:

l. A brake shoe comprising a body and a dry reenforce embedded therein,said reenforce being free in the body but anchored therewith and capableof limited relative movement therein.

2. A brake shoe comprising a body and a dry reenforce back embeddedtherein, said reenforce back being free in the body but anchoredtherewith and capable of limited relative movement therein.

3. A brake shoe comprising a body and a dry reenforce embedded in thewearing part thereof, said reenforce being free in the body but anchoredtherewith and capable of limited relative movement therein.

A brake shoe comprising a body and a dry reticulated metal reenforceembedded in the wearing part thereof, said reenforce being free in thebody but anchored therewith and capable of limited relative movementtherein.

5. A brake shoe comprising a body and a dry expanded metal reenforceembedded therein, said reenforce being free in the body but anchoredtherewith and capable of limited relative movement therewith.

6. A brake shoe comprising a body and a dry reenforce consisting of abundle of expanded metal embedded in the wearing part thereof, saidreenforce being free in the body but anchored therewith and capable oflimited relative movement therein.

7. A brake shoe comprising a body and a dry reenforce embedded therein,said reenforce being free in the body to permit strains upon thereenforce when the body fractures to be distributed over the reenforcefor a considerable distance from the line of fracture.

8. A brake shoe comprising a body and a dry reenforce embedded therein,said reenforce being free over its entire area in the body to permitstrains upon the reenforce when the body fractures to be distributedover the reenforce for a considerable distance from the line offracture.

9. A brake shoe comprising a body, a dry reenforce embedded in the backand a dry reenforce embedded in the wearing part of the body, saidreenforces being free in the body to permit strains upon them when thebody fractures to be distributed for a considerable distance over thereenforces from the line of fracture.

l0. The method of making a brake shoe which consists in applying to areenforce a coating comprising a refractory material and a bond,subjecting the coated reenforce to a baking heat and then arranging thereenforce in a mold, and pouring molten metal into the mold to form thebrake shoe with the reenforce embedded therein, the heat of the moltenmetal destroying the bond of the coating and leaving the refractorymaterial in a disintegrated state about the reenforce.

1l. The method of making a brake shoe which consists in applying to areenforce a coating comprising silica flour and a bonding oil of highviscosity, subjecting the coated reenforce to a baking heat and thenarranging the reenforce in a mold, and pouring molten metal into themold to form the brake shoe with the reenforce embedded therein, theheat of the molten metal destroying the bond of the coating and leavingthe refractory material in a disintegrated state about the reenforce.

ROBERT B. POGUE.

